1. Field of the Invention
This invention relates to rotary wood chippers for reducing wood materials into chips and more particularly to woodchippers with an improved wear block configuration.
2. Description of the Prior Art
In tree trimming or removal operations, limbs and other scrap wood material must be disposed of, which in the past has been accomplished by burning the scrap wood or delivering it to a landfill. In populated areas, burning undesirably increases the pollution content of the air. Shipment to landfill is expensive and the amount of available space for landfill disposal is becoming increasingly limited. Recently, the scraps have been reduced to wood chips which can then be employed for paper manufacture or, in some cases, used as a mulch around shrubs and the like. It is not generally feasible, however, to truck the wood scraps to a mill for processing in wood chippers since the expense of the gathering and shipping frequently outweighs the value of the resulting wood chips.
Some wood chippers have been designed which are portable and which are capable of processing at least small branches into wood chips which then can be gathered at the site of the tree trimming operation or can be distributed on the ground whereupon the chips will decay naturally without causing environmental damage. Some existing portable wood chippers, however, are generally not capable of handling relatively large limbs or medium sized trees (i.e., with diameters up to 15 inches). This problem is due to the relatively lightweight construction of the trailer-hauled portable wood chippers which are designed primarily for very small branches and not general duty purposes. On the other hand, existing wood chippers which are designed for larger pieces of wood material are extremely heavy and cannot easily be transported; or in cases where heavy duty chippers have been mounted on large trailers, the cost of the unit is prohibitive for small operators. Thus, there existed a need for a relatively heavy duty and yet portable chipper unit which was not overly costly.
U.S. Pat. No. 3,844,489 issued Oct. 29, 1974 disclosed an improved wood chipper comprising a generally rectangular chipping block having at least one aperture extending through the block and a chipper knife positioned on the edge of the aperture. Positioned on flat top and bottom edges of the rectangular block are chip clearing fan blades. The chipping block is enclosed and rotatably mounted in a housing which has an input aperture on one face for receiving material to be chipped and a discharge chute extending tangentially from the periphery thereof for removal of wood chips. The housing is mounted on a suitable framework at an acute angle relative to the direction of feed such that the chipper knife tends to draw the material into the chipper. Thus, a chipper with such a configuration is known as a slant disk wood chipper. Rotation of the chipping block is facilitated by a rotary shaft mounted between a pair of bearing block assemblies bolted to the outside of the housing. The bearing assemblies are of conventional design. A wear block also sometimes referred to as an anvil, having hardened wear surfaces, is horizontally mounted at a lower portion of the input aperture in closely spaced relationship to the chipper block. Material being fed into the chipper rides over the anvil which supports the material as the chipper knife slices the material into chips. Chip size is determined by adjusting the position of each knife in the chipping block. Prior art wood chippes of the type disclosed in the '489 patent and sold by strong Mfg. Co. incorporated a horizontal anvil that was adjustably mounted at a lower portion of the input aperture. The anvil could therefore be positioned to maintain appropriate tolerance with respect to the chipper knives.
In addition to drawing the material into the chipper, the rotating chipper block tends to force some of the material laterally toward the axis of rotation where the material tends to bunch up against an inside edge of the input aperture. To facilitate the cutting action at the inside edge, a second wear block having hardened wear surfaces is typically welded to the edge at approximately a right angle to the horizontal anvil. Maintenance of such a secondary wear block is difficult. Sharpening the edge of the vertical anvil requires dismantling at least a portion of the chipper, or, alternatively, building up the edge in place from an awkward angle. In the first instance, the chipper is unusable for an extended period. In the second instance, a sufficiently sharpened edge is not possible. Likewise, adjustment of the secondary wear block to correspond to adjustment of the horizontal anvil is very difficult.